I have messed something up with packages. Trying to fix an X11 problem in Ubuntu 11.10, I've done several package additions and removals, that each pulled some combination of dependencies with them. I don't know what's supposed to be on my system, but as I keep trying to troubleshoot errors from screenshots not working, to 3d problems, to limitations of the number of desktops I have, to touch screen problems, I keep finding that important packages are still missing from my system, despite the fact apt-get says everything is fine.
Where can I find a comprehensive list of what ought to be installed on my system for ubuntu 11.10, so I can just sudo apt-get the whole darn thing?